1. Field of the Invention
This invention relates to a movable table unit for use in a precision printing machine, a precision processing machine, a precision manufacturing machine or the like, and more specifically to a movable table unit which is mounted movably relative to a table base plate along two axes intersecting each other and rotatably relative to an axis perpendicular to a plane formed by the two axes.
2. Description of the Related Art
As a movable table unit for use in the aforementioned precision printing machine, a precision processing machine, a precision manufacturing machine or the like, so-called XY table in which a movable table is mounted movably relative to a table base plate along two axes intersecting each other has been often used.
Conventionally, as a movable table unit for use in the precision printing machine, the precision processing machine, the precision manufacturing machine or the like, so-called XY table in which a movable table is mounted movably along two axes intersecting each other with respect to a table base plate has been often used. In this XY table, a work placed on the movable table is moved along two axes, X and Y axes independently. In the precision printing machine or the like, not only an operation for moving a printing work placed on the movable table along the two axes, but also an operation for rotating it around an axis perpendicular to a plane formed by the two axes are required depending on the case.
Therefore, as the movable table for use in the precision printing machine or the like, an apparatus called "XY.theta. table" has been used, in which the movable table is not only mounted movably along the two axes intersecting each other with respect to the table base plate but also rotatably around an axis perpendicular to a plane formed by the two axes.
The technology relating to this XY.theta. table has been already disclosed in, for example, Unexamined Published Japanese Patent Application No.HEI8-99243, Unexamined Published Japanese Patent Application No.HEI1-240246, Unexamined Published Japanese Patent Application No.HEI1-242989, Unexamined Published Japanese Patent Application No.HEI4-210347, Unexamined Published Japanese Patent Application No.HEI8-211173, Unexamined Published Japanese Patent Application No.HEI8-252733, Unexamined Published Japanese Patent Application No.HEI9-42405, Unexamined Published Japanese Patent Application No.HEI9-155666, Unexamined Published Japanese Patent Application No.HEI9-216138, Unexamined Published Japanese Utility Model Application No.2515316, Unexamined Published Japanese Patent Application No.HEI4-354637, Unexamined Published Japanese Patent Application No.HEI6-31563, Unexamined Published Japanese Patent Application No.HEI7-219636, Unexamined Published Japanese Patent Application No.HEI5-77125, Unexamined Published Japanese Patent Application No.HEI4-2435, Unexamined Published Japanese Patent Application No.HEI3-56895, Unexamined Published Japanese Patent Application No.HEI2-202031, Unexamined Published Japanese Patent Application No.SHO62-282294 and the like.
The XY.theta. tables will be explained about a typical example thereof. In the longitudinally/laterally moving rotation table unit according to Unexamined Published Japanese Patent Application No.HEI8-99243, a movable table is supported on a base movably in all directions through three XY linear guide systems and a driving force is applied to moving blocks possessed by these XY linear guide systems through an independent ball screw unit. A upper rail possessed by each XY linear guide system is fixed to a bottom surface of the movable table. Upper and lower blocks possessed by the XY linear guide system are connected to each other with pins and bearing such that they are freely rotatable.
In the movable table according to Unexamined Published Japanese Utility Model No.2515316, the movable table is supported freely movably in all directions through a thrust bearing on a base. Three driving units are mounted in directions perpendicular to each other and output shafts of these driving units are connected to the movable table through a joint.
However, the above described conventional arts have the following problems. That is, in case of the longitudinally/laterally moving rotation table unit according to the Unexamined Published Japanese Patent Application No.HEI8-99243, a movable table is supported freely movably in all directions through three XY linear guide systems on the base and a driving force is applied to each of moving blocks possessed by these XY linear guide systems through an independent ball screw unit. Therefore, to rotate the movable table at a position other than an original point or move the movable table in parallel after it is rotated by a predetermined angle, the three XY linear guide systems have to be moved by different amounts mutually relating to one another, so that the table motion control becomes complicated. Also, in case of the longitudinally/laterally moving rotation table unit according to Unexamined Published Japanese Patent Application No.HEI8-99243, there is another problem, because the rotation center of the movable table is deviated due to motions thereof in the XY directions; it is difficult to carry out such a processing as printing or the like on a work placed on the movable table by rotating the movable table while moving it linearly along an axis after the movable table is positioned in the XY plane. Additionally, in case of the longitudinally/laterally moving rotation table unit according to the aforementioned Unexamined Published Japanese Patent Application No.HEI8-99243, the movable table is supported freely movably in all directions through three XY linear guide systems. Thus, further problem is that when a work is mounted or dismounted on/from the movable table, the movable table cannot be moved largely along a single axis even if it is requested.
On the other hand, in case of the movable table according to the aforementioned Unexamined Published Japanese Utility Model Application No.2515316, the movable table is supported movably in all directions through a thrust bearing on the base and three driving units intersecting each other are mounted on the base. Then, output shafts of the driving units are connected to the movable table through a joint. To rotate the movable table at a position other than an original point or move the movable table in parallel after it is rotated by a predetermined angle, the three driving units have to be moved by different amounts mutually relating to one another, so that the table motion control becomes complicated. Further, this invention has a problem that the rotation center of the movable table is deviated because of motions thereof in the XY directions and further has a problem that the movable table cannot be largely moved along an axis.